Pleiotropic Genes In Chickens (IMAGE) Linköping University Caption Three eighth generation advanced intercross siblings, demonstrating the extreme variation present in a cross between red jungle fowl and domestic chicken. LiU researchers have in this study discovered two 'pleiotropic' genes that influence both comb size and bone mass, and thereby also egg production. Credit Dominic Wright Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.